engleski

Prioritizing fishery management for loggerhead turtle (Caretta caretta) conservation in the northern Adriatic Sea from reproductive value analysis

Fisheries bycatch often affects particular size classes of turtles. Because of the late age at maturity, the reproductive value (RV) of small juvenile, large juvenile and adult loggerheads vary by orders of magnitude. RV provides a relative measure of value for individuals, thereby allowing us to estimate the effects of different stressors based on the number of animals killed. Using RV as a comparative index, we assessed the relative impact of trawl and gillnet fisheries operating in the northern Adriatic Sea on loggerhead populations. We tested several scenarios for bycatch in both fisheries which significantly differs in the size of captured animals and mortality. Despite high bycatch rates, bottom trawl fisheries result in direct death of fewer loggerheads (156-260 vs. 346-486 in gill nets), but affect individuals that are older and hence have higher RVs. Because of data limitations for vital rates and bycatch estimates, we looked at a distribution of potential impact for each fishery. Lessons learned include the need for relative impact assessment because of the sensitivity of adult RV to parameters such as clutch frequency, sex ratio and remigration interval. We anticipate that our analysis will help managers prioritize needs for regulation and mitigation among different fisheries.

bycatch; sea turtles; population modelling; reproductive value; conservation

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